The major objective of the proposed research is the comparative analysis of the transition in the mortality of Mexican American and "Anglo" (non-Hispanic white) infants over the past fifty years. To accomplish this aim, we will develop a unique data base of matched infant death and birth records that will permit a broader investigation of the mortality experience of Mexican American infants than has heretofore been possible (We propose to make this data set available to other researchers following the completion of the project.) Using this data base, we will demonstrate differences in the trends in infant mortality by examining the relationships between mortality risks during the neonatal and postneonatal ages and a number of factors including birth weight and other characteristics of infants, characteristics of their mothers and fathers, and circumstances of pregnancy and parturition. The research has the following specific aims: 1) To develop a file of linked birth and infant death records for the interval 1935-1985 which are coded systematically for all conditions (multiple causes) listed as leading to death, using a single disease classification, and comparably coded according to ethnic identification; 2) To trace trends in Spanish surname and non-Spanish surname infant mortality risk for both neonatal and postneonatal deaths, based on cause specific data for 1935-85 and both cause-specific and weight-specific data for 1949-85; 3) To identify discontinuities in cause of death codes associated with revisions of the International Classification of Diseases; 4) To determine whether the current favorable birth weight distributions among Mexican Americans existed in previous decades; 5) To determine the extent to which the major improvement in survivorship of Spanish surname infants, relative to other white infants, is associated with birth weight distributions and cause versus birth weight specific mortality risks. The source of the data for the proposed study is the birth and death certificates in the custody of the San Antonio Metropolitan Health District. Death records have already been acquired and are currently being coded for multiple causes of death and demographic characteristics as part of our ongoing project on mortality among Mexican-Americans and Mexican immigrants.